Lawyers at Milberg LLP, a large, nationally known firm, joined Paul Ceglia's legal fight three months ago in what was seen as a boost to the Buffalo man's claim, The Buffalo News reported Thursday.
Milberg is now dropping out, and Orin Snyder, one of Facebook's attorneys, said it was another sign the lawsuit has no bearing.
"The revolving door of lawyers is yet additional evidence that this abusive lawsuit is a hoax and a fraud," Snyder said.
Ceglia's lawsuit alleges he has a contract that entitles him to half of Zuckerberg's share of Facebook, worth billions.
Milberg is one of nine law firms that have abandoned Ceglia's case, though most of them never formally signed on to represent him, the News said.
Ceglia's attorney, Dean Boland, said Milberg's departure should not be seen as a vote of no confidence.
"They firmly believe in the evidence and the credibility of the case," Boland said. "They simply thought it was best for Paul that they no longer serve as a distraction."